1. Field of the Invention
The field of the invention pertains broadly to improvements in marine cargo transport and handling systems. More particularly, this invention relates to a system for efficient and expeditious handling of containerized cargo in a vessel having vertical storage compartments using a cargo transport vehicle having an improved collecting means for lowering and raising containers in the ship's hold from the main deck. The cargo vessel has an entrance way in the bow section to allow passage of the transport vehicle on and off the main deck for loading and unloading the cargo.
2. Description of the Prior Art
There are a variety of marine cargo handling systems which are used conventionally for ships having vertical storage compartments. These systems use either a movable or stationary crane, or other lifting device, on the dock in the harbor, or a crane mounted on a gantry which moves on tracks over the main deck of the ship. The systems requiring a harbor crane capable of being operated between the dock and the deck of the ship are costly from several viewpoints. Special and precise handling are required to ensure the proper alignment of the container carried by the crane with the hatchway opening in the ship which is most of all time-consuming, not to mention hazardous when attempted in adverse weather conditions. Moreover, container cargo trucks, either the conventional "side loaders" or "front loaders" are also needed to transport the cargo from the ground storage area to the harbor crane operating area. A harbor crane must operate over substantially the entire length of the main deck, and therefore, the side of the cargo ship must be positioned adjacent a relatively large portion of the dock. The dock space required further increases costs in view of the resulting harbor back-up which forces waiting ships to pay added harbor use charges. Since harbor crane systems do require substantial docking facilities, i.e. long enough to accommodate the ship's length and strong enough to bear the weight and movement of the heavy crane machinery, the overall usefulness and availability of the system is limited to relatively large ports.
Vessels equipped with a main deck gantry and crane apparatus suffer cost and structural drawbacks similar to those of the harbor crane systems. The gantry must be capable of traveling, such as on tracks, over the main deck and, therefore, must be a permanent part of the ship's structure. This increases the ship's cost and the operating expense of the system since each ship of the fleet must be comparably equipped and maintained. A cargo transport vehicle is still necessary either to move the cargo directly on and off the vessel or to a dock crane which can load and unload the cargo handled by the gantry crane. In those gantry vessels which are presently constructed to permit the passage of cargo transport vehicles onto the deck, or to some loading area on the vessel, stern entrance ways require special and costly arrangements of the vessel's control and operation facilities and, due to limited stern ballast tank volume, trimming is so restricted that loading and unloading is prohibited except under proper tidal conditions. On the other hand, in vessels which have previously been designed with bow opening, it has been necessary to reduce substantially the deadweight or cargo area of the ship to achieve an acceptable watertight bow structure.
These are other systems presently in use for handling marine cargo where the hold of the ship is divided into horizontal storage compartments extending lengthwise of the vessel. These systems employ either a main hatchway on the deck, extending vertically through each of the lower decks, or an open loading compartment at one end of the ships, for access to the storage compartments. In these horizontal stowage systems, either the loader vehicle must travel into the hold or some type of mechanized conveyor or railway system is required to transport the cargo unit from the pick-up and discharge area to its storage position for loading, and then back again for unloading. It will be seen that even the simplest of such systems is costly to operate and maintain, and furthermore, would reduce the available cargo area.
Thus, a continued need has existed to provide an efficient and economical system for handling containerized cargo without the need for any special port or docking facilities, or expensive on board handling apparatus, and without restriction of work time depending upon tidal or weather conditions.